Will, you may have seen this on Gaugemate's site...I found it helpful.

http://www.gaugemate.com/images/stor...sticstests.pdf

I had a couple of Parker hammer guns and one had 2 5/8" chambers that didn't have a forcing cone, just a sharp step. Your shells do look like you have shorter chambers.

the gauge mates are great way to make one gun into several guns...charlie